Hmm. I just had a closer look at the manual @ smokerstore.
The GT4 S has some VMQ silicone o-rings, but the GT 4 is all NBR nitrile rubber o-rings.
Not completely sure if the material matters much but perhaps it could help with the spinning of the juice flow control.
Also, could not find #3 and #18 in the GT4 S, in the GT4.